1. Field of Invention
The invention relates to an electrical measurement means, with at least one measurement input, at least one preferably integrated sensor, a measurement and evaluation circuit, at least one measured value display, and at least one measured value output.
2. Description of Related Art
The electrical measurement means according to the invention can be used to measure and process physical quantities (for example, pressures), temperatures, chemical quantities (for example, pH values), and electrical quantities (for example, voltages, currents, wattages and frequencies). One primary such electrical measurement mean is described below. It is used to measure and process pressures.
Electrical measurement means of the type under consideration can consist of several components, or can be made as a single-component measurement device. For the teaching of the invention, it is irrelevant whether the electrical measurement means in question consists of several components or is made as a single-component measurement device. An electrical measurement means is described below which consists of several components. Likewise, this measurement means can also be made as a single-component measurement device, wherein all components can be combined physically and spatially in one measurement device.
At this point, the initially used concepts xe2x80x9cmeasurement input,xe2x80x9d xe2x80x9csensor,xe2x80x9d xe2x80x9cmeasurement and evaluation circuit,xe2x80x9d xe2x80x9cmeasured value display,xe2x80x9d and xe2x80x9cmeasured value outputxe2x80x9d will be explained.
xe2x80x9cMeasurement inputxe2x80x9d means the location of the measurement means (or the measurement device) at which or via which the quantity to be measured, hereinafter always called the measured quantity, is supplied to the measurement means (or the measurement device). A xe2x80x9csensorxe2x80x9d means a component which generate an intermediate value from a measured quantity. The intermediate value is generally proportional to the measured quantity. If the measured quantity is a pressure, the sensor can generate an electrical voltage, for example, as the intermediate value. Alternatively, the sensor can also generate an electrical current, a resistance value, a capacitance value, or an inductance value as the intermediate value.
It was stated initially that the electrical measurement means according to the invention includes at least one sensor which is preferably integrated. It should be noted that when the electrical measurement means according to the invention includes several sensors, one sensor can be a separate component, but all sensors can also be separate components. When the measurement means of the invention includes several sensors, one sensor can also be integrated, but all sensors can also always be integrated.
The xe2x80x9cmeasurement and evaluation circuitxe2x80x9d which is included in the electrical measurement means in accordance with the invention is used to convert either the intermediate value generated by the sensor directly into a measured value, or to make available the measured value after processing the intermediate value as a measured value.
The measured value made available by the measurement and evaluation circuit can be displayed by the xe2x80x9cmeasured value displayxe2x80x9d in analog or digital format and can be made available at the xe2x80x9cmeasured value output.xe2x80x9d Generally, the measurement and evaluation circuit generates the measured value derived from the intermediate value in xe2x80x9celectrical form,xe2x80x9d for example, as a voltage proportional to the measured value between 0 V and 10 V. It may also be generated from a current proportional to the measured value between 4 mA and 20 mA or between 0 mA and 20 mA. If the measurement and evaluation circuit generates a voltage proportional to the measured value or a current proportional to the measured value, the measured value display is working in an analog form and there is an analog measured value. But the measurement and evaluation circuit can also generate the measured value which corresponds to the intermediate value in digital form. Additionally, it is also possible to work with a measurement and evaluation circuit which makes available both a measured value which corresponds to the intermediate value in analog form and also a measured value which corresponds to the intermediate value in digital form.
It is often necessary to xe2x80x9cusexe2x80x9d the measured value that is determined with an electrical measurement means of the type under consideration in mechanical device or means or in a process engineering system. When used in this fashion, the measured value is often dependent upon other values, such as comparison values or set points. Examples include difference pressure measurement, in which two certain measured values which represent pressure or two pressure-proportional measured values are needed, or a control means in which a quantity or measured value representing the present state is compared to a reference variable. To accomplish this in the prior art, relatively complex solutions were employed partially relying on a mechanical or physical basis, and partially relying on an electrical basis.
To overcome the problems in the prior art, the object of the invention is to make available an electrical measurement means with which not only one measured value or several measured values can be determined, but which makes it possible in an especially simple manner to display and optionally process the determined measured value or determined measured values depending on other values, for example comparison values or setpoints.
To achieve the object, the measurement means is characterized by at least one influencing input which acts on the sensor or on the measurement and evaluation circuit. The xe2x80x9cinfluencing inputxe2x80x9d is one such connecting point of the electrical measurement means to which or via which the xe2x80x9cinfluencing valuexe2x80x9d can be applied or input. The influencing input is a value with which the measured value or measured values can be influenced in the broadest sense. The influencing input, the sensor, and the measurement and evaluation circuit can be sensitive to electrical, optoelectronic, optical, pneumatic or hydraulic influencing values. When the electrical measurement means has several influencing inputs, the influencing inputs can be of different electrical sensitivity. Thus, at least one influencing input can be electrically sensitive, at least one influencing input can be optoelectronically or optically sensitive, and at least one influencing input can be pneumatically or hydraulically sensitive. The formulation xe2x80x9csensitive to electrical influencing valuesxe2x80x9d or the formulation xe2x80x9csensitive to optoelectronic and/or optical influencing valuesxe2x80x9d means that the influencing value can be present in electrical form or in optoelectronic or optical form.
Since the electrical measurement means, as explained above, includes an influencing input, to which or via which a influencing value can be applied or input, the electrical measurement means also includes an influencing value selector. That is, a component, device or means with which the influencing value to be used at the time is generated or selected. Preferably, this influencing value selector is external and separate from the remaining measurement means, and is connected to the remaining measurement means via an electrical line, via an optical line, or via a pressure line.
In alternative embodiments, the influencing value selector can be made differently, especially to work passively or actively.
If the influencing value selector is made to work passively in the electrical measurement means, the influencing value generated or selected by it must be interrogated or read out, proceeding from the influencing input of the measurement means. A passively working influencing value selector can provide a resistance, capacitance, or inductance value which represents the influencing value, to be interrogated or read out.
An actively operating influencing value selector can apply a voltage value to the influencing input of the electrical measurement means. The voltage value represents the influencing value or can impress a current value which represents the influencing value. It is also possible to use one such influencing value selector which delivers a pressure to the influencing input. The pressure represents the influencing value via a pressure line.
The electrical measurement means may include an influencing value selector made to work actively, and therefore require electrical energy. This electrical energy can be supplied independently to the influencing value selector from the remaining measurement means. The electrical energy required by the actively working influencing value selector can be supplied to it by the remaining measurement means. This is recommended because the influencing value selector must be connected to the remaining measurement means. It is further recommended that the influencing value be transmitted via the connecting line between the influencing value selector and the remaining measurement means. The electrical energy required by the influencing value selector must also be transmitted from the remaining measurement means to the influencing value selector. The connecting line can be a two-wire line because both information and energy can be transmitted via a two wire line.
Otherwise, the influencing input can preferably be made as a standardized analog input, for example for an influencing value from 0 V to 10 V, from 4 mA to 20 mA or from 0 mA to 20 mA. This has the advantage that a host of sensors available on the market can be used as the influencing value selector.
The influencing value selectors can also be especially xe2x80x9ccheap sensors,xe2x80x9d that is those which do not have a measured value display or any mechanical adjustment elements.
In the subject measurement means, the actual sensor, here called the main sensor, and the influencing value selector, here called the secondary sensor, can preferably be made cylindrical and be provided with plug connections. This has advantages for connection and terminal engineering.
The subject electrical measurement means integrated sensor is preferably a so-called xe2x80x9cintelligentxe2x80x9d sensor, that is a sensor which can be programmed or parameterized. Then the important teaching of the inventionxe2x80x94influencing inputxe2x80x94easily enables programming and parameterization of the sensor with a corresponding influencing value via the influencing input.
In the embodiment of the electrical measurement means in which there is an influencing input acting on the sensor, the influencing value can be used not only to program or parameterize the sensor, but also to otherwise influence the sensor. In particular, the transmission characteristic of the sensorxe2x80x94dependency of the intermediate value generated by the sensor on the measured quantityxe2x80x94can be influenced. For example, if the transmission characteristic is not linear, it can be linearized. Further, an actually linear transmission characteristic can be influenced such that after influencing, it has a degressive or progressive characteristic. It is also possible to suppress from the transmission characteristic the initial range, or the end range, or both an initial range and also the end range, so that there is a transmission characteristic as in a high pass filter, lowpass filter, or a bandpass filter.
Especially when it is possible to act on the measurement and evaluation circuit via the influencing input provided in the electrical measurement means, there are further possibilities for achieving different results via different influencing values.
Difference pressure measurements and other control means are examples of the fact that determined measured values may depend on other values such as comparison values or set points. The difference necessary for this purpose can be determined by subtracting the value input as a constant quantity or by subtracting this value as a variable quantity, that is, as a quantity which varies over time, via the influencing inputxe2x80x94as the influencing value. It is also possible to input a multiplying value or a dividing value as the influencing value via the influencing input. In this manner, a value may be input with which the intermediate value derived from the measured quantity is multiplied or divided. The measured value can thus be spread or compressed. An influencing value is also conceivable which leads to the measured value being inverted, therefore a value being delivered to the measured value display or a value being present on the measured value output to which the inverse of the measured value corresponds.
The subject electrical measurement means preferably includes at least one measured value output so that the measured value can be read out not only using the measured value display, but also so that the measured value is available via the measured value output in order to be displayed elsewhere and xe2x80x9cto be usedxe2x80x9d in some other way, for example, in a mechanical device or means or in a process engineering system, such as in a control means of one such process engineering system.
The electrical measurement means is generally provided with several measured value outputs. Whether there are multiple measured value outputs or not, it is recommended that at least one measured value output be made to work analog and at least one measured value output be made to work digital, or at least one measured value output be made to work as a switching output. In the embodiment of the subject electrical measurement means, the measured value output is made as a switching output. The operating threshold can be input by a corresponding influencing value via the influencing input of the subject invention. Using a corresponding influencing value, via the influencing input, a certain hysteresis behavior can be impressed on the measured value output at a switching output. This hysteresis behavior can also be effective depending on the measured value. Otherwise, using a corresponding influencing value with a nonparallel displacement of the operating point hysteresis line can be accomplished so that the hysteresis becomes greater as the measured value increases, therefore a funnel-shaped characteristic results.
It has already been explained above that different influencing values can take effect via the influencing input in the electrical measurement means. These inputs provide for implementing quite different measures. This is addressed below.
In the subject electrical measurement means, there can be a single influencing input. Nevertheless, difference measures can be achieved with different influencing values, by influencing the sensor, by influencing the measurement and evaluation circuit, and by influencing the sensor and the measurement and evaluation circuit. To do this, a branching component can be connected downstream of the single influencing input. The branching component delivers influencing values below a certain influencing threshold only to the sensor, and influencing values above a certain influencing threshold only to the measurement and evaluation circuit. It is also possible to operate the sensor and the measurement and evaluation circuit in different fashions such that the sensor is sensitive only to influencing values below or only to influencing values above a certain influencing threshold, and the measurement and evaluation circuit is sensitive only to influencing values above a certain influencing threshold or only to influencing values below a certain influencing threshold. In addition, the sensor and the measurement and evaluation circuit can be influenced in a time-dependent fashion. In this version, then, the sensor resets to an influencing value only when this influencing value is below or above a time threshold. Likewise, the measurement and evaluation circuit responds to an influencing value only when it is above or below a time threshold.
Allowing different influencing values to take effect, whether on the sensor or on the measurement and evaluation circuit, can be accomplished by the subject electrical measurement means having several influencing inputs, such as at least one influencing input for the sensor and at least one influencing input for the measurement and evaluation circuit.
In the subject electrical measurement means, the influencing value or the influencing values can represent the same physical quantity as the measured quantity; this applies in difference pressure measurement or in conjunction with the control means in which a measured quantity or a measured value represents the present state, or where a reference variable is required. However, it is also possible to derive the influencing value or the influencing values from a physical quantity other than the measured quantity. For example, when a pressure is to be determined as the measured quantity, an influencing value can be formed as a function of temperature in order to implement temperature-dependent pressure compensation. An influencing value can also be implemented as a function of temperature, pressure or flow.
Finally, it should be point out that in the electrical measurement means, the measurement and evaluation circuit can also assume very complex functions. For example, in the measurement and evaluation circuit a Proportional Integral Derivative PID control algorithm can be implemented, so that at the measured value output, an analog manipulated variable for an analog operating actuator is available as the output signal, such as for an analog operating pressure value.
In particular, there are various possibilities for embodying and developing the electrical measurement means as claimed in the present invention. To do this, reference is made both to the claims dependent on claim 1 and also to the description of the preferred embodiment of the electrical measurement means according to the invention shown in the drawings.